Selective block in erythropoietin-induced differentiation of growth factor-independent retrovirally-infected TF-1 cells

The erythroleukaemic cell line TF-1, infected with either the pBabe neo retrovirus or the retrovirus bearing the human erythropoietin (hEpo) gene, developed three growth factor-independent clones. Erythropoietin (Epo), interleukin-3 (IL-3) and granulocyte-macrophage colony stimulating factor (GM-CSF) accelerated the proliferation of these clones. Autonomous growth of the clones was independent of Epo because it was not altered by Epo anti-sense oligonucleotides, nor was Epo detectable in culture supernatants. Cells from the mutant clones could not be induced by Epo to express glycophorin A and haemoglobin synthesis was markedly reduced. Haemin reversed the block in Epo-induced haemoglobin synthesis. Acquisition of growth factor-independence appears to be linked with the selective loss of differentiation capacity. These cells may provide a useful model for the study of the mechanisms involved in leukaemic transformation.

A probabilistic modelling scheme for analysis of long-term failure of cemented femoral joint replacements

Reliable prediction of long-term medical device performance using computer simulation requires consideration of variability in surgical procedure, as well as patient-specific factors. However, even deterministic simulation of long-term failure processes for such devices is time and resource consuming so that including variability can lead to excessive time to achieve useful predictions. This study investigates the use of an accelerated probabilistic framework for predicting the likely performance envelope of a device and applies it to femoral prosthesis loosening in cemented hip arthroplasty.
A creep and fatigue damage failure model for bone cement, in conjunction with an interfacial fatigue model for the implant–cement interface, was used to simulate loosening of a prosthesis within a cement mantle. A deterministic set of trial simulations was used to account for variability of a set of surgical and patient factors, and a response surface method was used to perform and accelerate a Monte Carlo simulation to achieve an estimate of the likely range of prosthesis loosening. The proposed framework was used to conceptually investigate the influence of prosthesis selection and surgical placement on prosthesis migration.
Results demonstrate that the response surface method is capable of dramatically reducing the time to achieve convergence in mean and variance of predicted response variables. A critical requirement for realistic predictions is the size and quality of the initial training dataset used to generate the response surface and further work is required to determine the recommendations for a minimum number of initial trials. Results of this conceptual application predicted that loosening was sensitive to the implant size and femoral width. Furthermore, different rankings of implant performance were predicted when only individual simulations (e.g. an average condition) were used to rank implants, compared with when stochastic simulations were used. In conclusion, the proposed framework provides a viable approach to predicting realistic ranges of loosening behaviour for orthopaedic implants in reduced timeframes compared with conventional Monte Carlo simulations.

The effect of construction pattern and unit interlock on the structural behaviour of block pavements

The maintenance or even replacement of cracked pavements requires considerable financial resources and puts a large burden on the budgets of local councils. In addition to these costs, local councils also face liability claims arising from uneven or cracked pedestrian pavements. These currently cost the Manchester City Council and Preston City Council around £6 million a year each. Design procedures are empirical. A better understanding of the interaction between paving blocks, bedding sand and subbase was necessary in order to determine the mode of failure of pavements under load. Increasing applied stress was found to mobilise ‘‘rotational interlock’’, providing increased pavement stiffness and thus increased load dissipation resulting in lower transmitted stress on the subgrade. The indications from the literature
review were that pavements are designed to fail by excessive deformation and that paving blocks remained uncracked at failure. This was confirmed with experimental data which was obtained from tests on segments of pavements that were laid/constructed in a purpose built test frame in the laboratory.

IMPROVED POSTFILTERING TECHNIQUE FOR BLOCK QUANTISATION OF SPEECH.

A modified comb filtering technique is proposed which can be used to reduce framing noise generated when speech signals are transform-coded or vector-quantized. Application of this filter to 9. 6 kbit/s speech in a vector transform coder has been found to improve the perceptual quality of the coded speech.

Systolic building block for high performance recursive filtering

A novel bit level systolic array is presented that can be used as a building block in the construction of recursive digital filters. The circuit accepts bit-parallel input data, is pipelined at the bit level, and exhibits a very high throughput rate. The most important feature of the circuit is that it allows recursive operations to be implemented directly without incurring the large m cycle latency (where m is approximately the word length) normally associated with such systems. The use of this circuit in the construction of both first- and second-order IIR (infinite-impulse-response) filters is described.

The mechanical effect of the existing cement mantle on the in-cement femoral revision

Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.